The Allen-Mercury (A-M) range from England was the brain-child of Dennis Allen, a prominent member of the West Essex model flying club who had a long association with model engines going back to the late 1940's when he operated the engine repair service offered by the well-known model shop Henry J. Nicholls Ltd. of 308 Holloway Road, London. Subsequently, Allen worked for Alan Allbon and the later makers of the AMCO range before striking out on his own in 1954. He traded under the name D.J. Allen Engineering Co. from premises in Edmonton, North London.

Beginning with the 1954 A-M 25 Mk. I, Allen progressively introduced a range of well-made model diesels in 1 cc, 1.5 cc, 2.5 cc and 3.5 cc nominal displacements. His firm also released a 0.81 cc glow-plug model which was more or less a clone of the American Wen-Mac .049.  In fact, the A-M .049 (as this model was known) was almost certainly nothing more than a "badge engineered" Wen-Mac product.

In mid 1961, Allen's company took on the manufacture of the Merco glow-plug range which had been introduced in 1959 by Bill Morley and Ron Checksfield. Thereafter, the firm passed through a series of ownership changes while still maintaining A-M and Merco production into the new millenium.

An article summarizing the full history of the A-M range and its merger with Merco may be found elsewhere on this website.